1. Field of the Invention
The present invention generally relates to an original data circulation method, system apparatus, and computer readable medium. More particularly, the present invention relates to providing technologies for storing and distributing data such as a digital ticket which represents a digital right, digital contents and the like, in which the number of valid reproductions of such data needs to be smaller than a defined number.
2. Description of the Related Art
Reproductions of data or a digital ticket which represents a digital right exceeding the number which the data distributor intends should be prevented. That is, distributed data that is reproduced by a user illegally should be prevented.
Conventionally, such multiple use is prevented by technologies described in the following.
A first method is that transfer histories of the original data are attached to the data and they are used to check whether the data is already used or not at the time of request for exercising the right. If the right is already used up, the service provider (or collector) of the data refuses accepting the right represented by the data.
A second method is to store the data in a tamper-proof device such that the data cannot be accessed except via the tamper-proof device. When the data is used up, the data is deleted from the tamper-proof device.
According to the above-mentioned first method, a special device such as the tamper-proof device is not necessary. However, a problem comes up when the data is circulated. More specifically, validity of the data can be checked only when the right is exercised according to the first method. Therefore, there is a problem that the validity of the data can not be judged while the data is circulating.
According to the above-mentioned second method, uniqueness of the data can be protected by using the tamper-proof device. In addition, methods which are described in Japanese patent application No. 6-503913 or Japanese laid-open patent application No. 9-511350 can be used together with the above-mentioned second method, in which a plurality of tamper-proof devices are connected via secure communication routes which are protected by cryptography. The data is exchanged via the communication routes such that the data can be circulated while preventing reproduction of the data. However, the technology has the following two problems since the data needs to be stored in the tamper-proof device.
First, it becomes impossible to view the description of the data. Therefore, there is a constraint that all checks such as a check of the validity period of the description should be left to the tamper-proof device.
In addition, since the tamper-proof device should not only have a storing part of the data but also carry out all processing necessary for handling the data, a large storage capacity and a high processing throughput are required for the tamper-proof device. Especially, an IC card which is generally used for the tamper-proof device does not have enough storage capacity or processing throughput.